Means for regulating dynamo-electric machines.



No. 898,058. PATENTED SEPT. 8, 1908.

W. L. MERRILL. MEANS FOR REGULATING DYNAMO ELECTRIC MACHINES.

APPLICATION FILED FEB. 20, 1906.

W/Zfnes ses; //71 e/7t0/" Atty.

. ance of the line, generator armature and in Dynamo-Electric Machines, of which the UNITED sTnTEs grE T oEEIoE.

WILBUR L. MERRILL,

oEiso ENEcTADY, NEW YORK, ASSIQllQR TO GENERAL ELECTEIo COMPANY, A OQRPORATION or NEW YORK. s

. INEEANS FOB EEGULATING DYNAMIC-ELECTRIC MACHINES.

Specification of Letters Patent.

\ Patented-Sept.-8, 1908.

Application filed February 20, 1906. Serial No. 302,031.

To all whom it may concern:

Be it known that I, WILBUR L. MERRILL, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Means for Regulatfo owing is a specification.

The present invention relates to the regulation of dynamo-electric machines and more particularly generators forming part of n10- tor-generator sets supplying current to motors. 4

A common method of operating and controlling electric motors consists in supplying current to the motor from a generator which is in turn driven by a motor connected to the main source of current sup 1y. The ower and speed of the motor are t en control ed by varying the volta e of the generator, usually by increasing or decreasing the field excitation produced by a shuntwinding. In this arrangement, for any given field excitation of the generator, the motor to be operated and controlled would run at a uniform speed irrespective of the load, except for variation in potential losses due to the resistmotor armature, and reactions in the generator armature) These losses of course increase with the load, that is, with the current; and when, as frequently happens, the motor is removed at some consid erable distance from the motor-generator, the line loss is considerable. The potential loss due to the brush and armature resistance of the motor unit is likewise of importance where a plurality of motors are operated in series, for exam le. In addition to these losses in potentia the potential of the generator is lowered upon increase in load by reason of the slowing down of the motor which drives the generator;

It is customary to compound the enerator by providing an auxiliary series field winding which excites the field of the generator variously depending u on the current taken from the enerator. 1? current were to be supplied by the generator at one potential only,

tioned so as to com ensate for all the poten-' tial losses under di erent load, so as to maintain the speed of the motor uniform; but Where the generator is intended to supply current varying widely in voltage, this comounding, if proper for low volta es and arge currents, is insufi'icient for high voltages and large currents, by reason of the fact that the generatorfield is highly magnetized at high voltages and an increase in current in the series windin the same increase in field strength as is the case at lower voltages. Similarly, if the compounding is designed for most effective operation at high voltages the machine is over-compounded at low voltages.

The ob ect of the present invention is to provide means, in a system of the character described, whereby the voltage at the terminals of the motor to be operated and controlled may be automatica y maintained at a'value adapted to kee the speed of the motor substantially un' orm at any desired value within the limits determined by the range of voltage at which the generator may supply current;

To the above end I have provided the generator with a field winding which shall be energizedby the current flowin through the armature of the motor whic drives the generator. In this arrangement the magnetomotive force produced by this compounding winding varies directly with the oad on the system and is independent of the current taken by the motor to be controlled. On the lighter loads the field excitation increases approximately in the same ratio as the magnetomotive force, but onthe heavy loads, namely after saturation of the field magnets of the generator, the flux increases less rapidly than the magnetomotive force. Good compounding may be effected by utilizing the currents flowing through both motors for exciting the generator, since on light loads, and conseuently with an unsaturated generator field, t e potential losses ma be taken care of-by currents supplied by t e generator, the exdoes not produce are pre The present invention is illustrated in the accompanying drawing wherem Figure 1 shows diagrammatically a motor generator system adapted to supply current -to and control the s eed and power of an electric motor, the w ole being arranged in accordance with the present invention; and Fig. 2 is a similar view showing a further modification.

Reference being had to Fig. 1 of the drawing, A indicates an electric motor and B a motor-generator for supplying current to the motor. The motor-generator comprises a motor I) having an armature c and field winding 0 and a generator I) havm an armature d and field windings d 2 and d shunt motor havingits armature and field windings connected in parallel across the supply mains 1 and 2. The motor A is situated at some distance from the motor generator, and its armature a is supplied with current from the generator throu 11 leads 3 and 4.- The field winding (1 may e energized by current from the suppl mains through leads 5 and 6. The .spee of the motor A is determined by the,voltage of the generator which is controlled by adjusting the rheostat 7 in the circuit of the main field winding d, preferably connected across the supply main. If it were not for the drop in potential in the leads 3 and 4, between the terminals of the motor and generator armature, and because of the lowering of the generator speed upon increase in load the speed of the motor would remain constant for any given setting of the rheostat 7,. irres ective of the load, but this drop in potentia varies directly with the current supplied by the generator. The field windings d and d of the generator serve to compensate for the drop in potential in the system from the various causes specified, the windin (1 being in series with the armatures'a and and the winding (Z being in series with the armature of the motor driving the generator. When the generator is adjusted to give current at a low voltage, the generator field does not become highly magnetized and therefore, by properly proportioning the windings d and the auxihary field excitation of the generator varies directly with the load; and, as

The motor I) is illustrated as a the line drop increases upon increase in curof the generator is gradually increased so as the terminals of the armature of the motor A,the effect of the winding (1 being relatively small. When the generator-is delivering current at ahigh potential, the line dro between it and the motor varies exact y as before, directly as the current varies.

rent taken by the motor I) is proportionately greater than on lower loads, and the efiect of manner not possible by the winding (1 In this way the load factor and the factor depending simply upon the current delivered y the generator at all times cooperate to provide a uniform increase of potential as difference in the reluctance of the magnetic circuit of the-generator under different conditions.

In 2 the motor I) of the motor-generator set is the same asin Fig. 1, but instead of having two regulating windings on the generator, 'asingle winding 41' is employed; this single winding being in series with boththe ture a. two armatures, after passing throu h the winding (1 branch at the point 3, one owin through the armature of the'motor A, an the other through the main supply circuit. Although but two modifications of the present invention have been illustrated, I do not desire to limit the present invention to these two modifications alone, since it is evident that the regulation of the generator of the motor-generator set by means dependent upon the load on the motor may be carried out in other ways than those illustrated.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. In a system of control, an electric motor, a motor generator set supplying current to said motor, means for varying the voltage of the generator of the motor generator set to vary the speed of said motor, and means for modifying the voltage of said generator so as to maintain a predetermined speed of said motor constant,.independent of its load.

2. In a system of controla source of current supply, a shunt motor with its field excited from said supply, a motor set driven to the armature of said motor, the generator of .said. motor generator set having a field winding with a variable resistance arranged to vary its voltage through wide limits, a

second in series with its armature rent supplied by the generator, the voltage to maintain a constandpotential between.

the current increases, notwithstanding. the.

from said current supply supplying current If the load on the system is heavy, the cur:

the d is increased, keeping pace with the mcreased reluctance of the magnetic circult of the generator due to saturation. in a generator armature d, and the motor arma- The currents flowing through thesecircuit and a third windin in series with its In witness whereof, I have hereunto set driving mfitor armaturel or maingaining a my hand this 19th day of February, 1906.

an stantia y constant v0 tage on t e enerator when running at high or low voltfige so WILBUR MERRILL 5 as to maintain a sfieed on the motor independ- Witnesses:

ent of its load, a the windings producing a BENJAMIN B. HULL,

flux in the same direction. HELEN ORF'ORD. 

